Microwave ovens operate by utilizing electromagnetic radiation in the microwave frequency range to heat food. The specific frequency used by microwave ovens is around 2.45 gigahertz (GHz), which corresponds to a wavelength of approximately 12 centimeters.
The interaction between the microwave radiation and water molecules in food is based on a phenomenon called dielectric heating or dipole rotation. Water molecules possess a permanent electric dipole moment, meaning they have a positive charge at one end and a negative charge at the other. In an alternating electric field, such as that generated by the microwave radiation, the water molecules attempt to align themselves with the changing electric field.
When the microwave radiation is applied, the electric field rapidly alternates its direction, causing the water molecules to rotate back and forth in response to the changing field. This rotation leads to the reorientation of the water molecules and generates molecular friction and kinetic energy.
As the water molecules rotate and collide with each other due to the oscillating electric field, this energy is converted into heat, which raises the temperature of the food. The heat generated by the molecular motion is then conducted to adjacent portions of the food, resulting in overall heating.
It's worth noting that while water molecules are primarily responsible for absorbing microwave energy, other molecules with electric dipoles, such as those found in fats and sugars, can also contribute to the heating process to some extent.
It is important to ensure that food is evenly heated in a microwave oven, as uneven heating can lead to hot spots or cold spots. This is why it is recommended to use microwave-safe containers, stir or rotate the food during heating, and allow for standing time after heating to distribute the heat uniformly.